Cylinder deactivation control system

ABSTRACT

A vehicle includes a transmission; a torque converter coupled to the transmission; a controller in communication with the transmission and the torque converter; a driver seat, a passenger seat, and a back seat coupled to the transmission; and sensors configured to detect user occupancy of the seats. The sensors are in communication with the controller. The controller is programmed to receive data from the sensors, determine an occupancy status based on the occupancy data, set an engine operating parameter of one of the transmission and the torque converter based on the occupancy status, and control one or both of the transmission and the torque converter to operate according to the parameter.

BACKGROUND

A powertrain of a vehicle includes an engine, a torque converter, and atransmission coupled in series. If the engine is an internal-combustionengine, the engine contains cylinders that serve as combustion chambersthat convert fuel to rotational kinetic energy. The torque convertertransmits rotational motion from the engine to the transmission whileallowing slippage between the engine and transmission, for example,while the engine is running and the vehicle is stopped. The transmissiontransmits the kinetic energy from the torque converter to a drive axleand ultimately to wheels of the vehicle, while applying a gear ratioallowing different tradeoffs between torque and rotational speed.

Noise, vibration, and harshness (NVH) constraints can limit the fueleconomy possible for the powertrain. Deactivating cylinders of theengine can increase the efficiency of the engine, but running the enginewith fewer cylinders can cause torque pulsations that are unpleasant foroccupants of the vehicle. Likewise, reduced slippage in the torqueconverter can increase the efficiency of the powertrain, but reducedslippage also transmits more vibrational shocks from the engine tooccupants. And finally, reducing the vehicle speeds at which gear shiftsoccur or gear ratios change can increase fuel economy but may alsoincrease the noise and vibrations experienced by occupants.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an example vehicle.

FIG. 2 is a graph of example transmission schedules.

FIG. 3 is a graph of example cylinder-deactivation schedules.

FIG. 4 is a block diagram of an example control system.

FIG. 5 is a process flow diagram of an exemplary process for adjustingthe efficiency and noise, vibration, and harshness characteristics ofthe vehicle of FIG. 1.

FIG. 6 is a process flow diagram of a second exemplary process foradjusting the efficiency and noise, vibration, and harshnesscharacteristics of the vehicle of FIG. 1.

DETAILED DESCRIPTION

With reference to the Figures, wherein like numerals indicate like partsthroughout the several views, a vehicle 30 includes a transmission 36; atorque converter 38 coupled to the transmission 36; a controller 60 incommunication with the transmission 36 and the torque converter 38; adriver seat 52, a passenger seat 53, and a back seat 54 coupled to thetransmission 36; and sensors 64 configured to detect user occupancy ofthe seats 52, 53, 54. The sensors 64 are in communication with thecontroller 60. The controller 60 is programmed to receive data from thesensors 64, determine an occupancy status based on the occupancy data,set an engine operating parameter of one of the transmission 36 and thetorque converter 38 based on the occupancy status, and control one orboth of the transmission 36 and the torque converter 38 to operateaccording to the parameter.

Setting the engine operating parameter based on the occupancy statusincreases the efficiency of the vehicle 30 at the expense of increasingnoise, vibration, and/or harshness (NVH) in situations in which theincreased NVH is less likely to be experienced by occupants. If thevehicle 30 is autonomous, then the vehicle 30 may be unoccupied, oroccupants may be seated only in the back seat 54 and not the driver orpassenger seats 52, 53, or an occupant may be seated in the passengerseat 53 and not the driver seat 52. Occupants of the back seat 54 may beless exposed to NVH from an engine 34, torque converter 38, andtransmission 36 than occupants of the driver or passenger seats 52, 53,and the occupants of the driver seat 52 and the passenger seat 53 mayhave different NVH exposures. Increased NVH has less downside in some ofthese occupancy statuses than others, so it becomes more acceptable totrade off NVH for greater efficiency of the vehicle 30.

The vehicle 30 may be an autonomous vehicle. In this context,“autonomous” means that each of vehicle 30 propulsion (e.g., apowertrain including an internal combustion engine), steering, andbraking are controlled by the controller 60 without human intervention.The controller 60, sometimes referred to as the “virtual driver,” may becapable of operating the vehicle 30 independently of the intervention ofa human driver, to a greater or a lesser degree, e.g., the vehicle 30could be operated semi-autonomously, meaning that one or two ofpropulsion, steering, and braking are controlled by the controller 60without human intervention. The controller 60 may be programmed tooperate the engine 34, the torque converter 38, the transmission 36, abraking system, a steering system, and/or other vehicle systems. Thecontroller 60 may have an autonomous mode, in which the controller 60operates the vehicle 30, and semi-autonomous and/or manual modes, inwhich a human driver operates some or all of the subsystems of thevehicle 30 pertaining to propulsion, steering, and braking.

As shown in FIG. 1, the vehicle 30 includes a passenger cabin 50 tohouse occupants, if any, of the vehicle 30. The passenger cabin 50includes a driver seat 52 and a passenger seat 53 disposed at a front ofthe passenger cabin 50 and one or more back seats 54 disposed behind thedriver and passenger seats 52, 53. The passenger cabin 50 may alsoinclude third-row seats (not shown) at a rear of the passenger cabin 50.In FIG. 1, the driver and passenger seats 52, 53 are shown to be bucketseats and the back seat 54 is a bench seat, but the seats 52, 53, 54 maybe other types. The seats 52, 53, 54 may be coupled to the transmission36, that is, directly or indirectly mechanically connected to thetransmission 36; specifically, the seats 52, 53, 54 may be coupled to aframe of the vehicle 30 (not shown), and the transmission 36 may becoupled to the frame. The position and orientation of the seats 52, 53,54 and components thereof may be adjustable by an occupant.

The vehicle 30 includes a powertrain 32, which includes the engine 34;the torque converter 38, which is coupled to the engine 34, that is,directly or indirectly drivably connected to the engine 34; and thetransmission 36, which is coupled to the torque converter 38. Thepowertrain 32 produces energy and converts the energy into rotationalmotion of wheels 44 that propel the vehicle 30.

The engine 34 may be an internal combustion engine, an electric engine,or a hybrid electric engine. In an internal combustion or hybrid engine,the engine 34 includes a plurality of cylinders 40.

The cylinders 40 operate as combustion chambers in which a chemicalreaction of a fuel translates into kinetic energy of a piston (notshown) of the cylinder 40. The pistons of the cylinders 40 are coupledto the torque converter 38 such that linear movement of the pistonsdrives rotational motion of the torque converter 38. The cylinders 40 ofthe engine 34 fire in a predefined sequence.

The engine 34 may use all of the cylinders 40 to power the vehicle 30 ormay use a set of active cylinders 40 including less than all thecylinders 40. FIG. 3 shows an example cylinder deactivation schedule.The deactivation schedule may be a function of the engine speed (cyclesper unit time) and the torque produced by the engine 34. In a region 302between threshold values of the engine speed and below a torque curve,some cylinders 40 are deactivated, and outside the region 302, allcylinders 40 are active. For example, if the engine 34 has six cylinders40, then only four cylinders 40 may be active if the engine speed andtorque are within the region 302.

The torque converter 38 is coupled to the engine 34 and to thetransmission 36. The torque converter 38 transmits rotational motionfrom the engine 34 to the transmission 36. The torque converter 38decouples the motion of the engine 34 from the motion of thetransmission 36, allowing the engine 34 to, for example, continuerunning while the vehicle 30 is stopped. When the vehicle 30 is moving,the torque converter 38 allows the engine speed to be higher than theinput speed of the transmission 36. The difference in speed across thetorque converter 38 from the engine speed to the input speed of thetransmission 36 is called “slip.” The torque converter 38 has a lock-upclutch that can reduce or eliminate slip by establishing a mechanicalconnection through the lock-up clutch to connect the engine 34 and thetransmission 36, thus allowing a variable slip. Using the lock-upclutch, the torque converter 38 can switch between an unlocked statewith a positive rate of slip and a locked state with zero rate of slip.In the unlocked state, the torque converter 38 allows slippage betweenthe engine 34 and the transmission 36, transmitting less rotation athigher torque from the engine 34 to the transmission 36. In the lockedstate, the torque converter 38 transmits all rotation from the engine 34to the transmission 36, so the transmission 36 rotates at the same speedas the engine 34. The lock-up clutch may be intermediately engaged toallow partial slipping.

A lock-up schedule lists the conditions under which the torque converter38 has different quantities of slip or is in the locked or the unlockedstate. The conditions are based on variables describing the state of theengine 34 or the vehicle 30, such as accelerator pedal position, vehiclespeed, the ratio of accelerator pedal position to vehicle speed, andother factors such as brake pedal position, engine speed, engine torque,engine temperature, transmission temperature, etc.

The transmission 36 is coupled to the torque converter 38, that is,directly or indirectly drivably connected to the torque converter 38.The transmission 36 transmits power generated by the engine 34 to adrive axle connected to wheels (not shown). The transmission 36 canchange the gear ratio between input from the torque converter 38 andoutput to the drive axle. The transmission 36 may be any suitable typeof transmission, including an automatic transmission with a set ofdefined gear ratios, called gears, or a continuously variabletransmission. At higher gear ratios or lower gears, the transmission 36transmits more torque at a higher engine speed to the drive axle, and atlower gear ratios or higher gears, the transmission 36 receives torquefrom the engine 34 at a slower engine speed for a given speed of thedrive axle and transmits less torque to the drive axle.

A transmission schedule determines the gear ratio of the transmission 36as a function of the vehicle speed and the position of an acceleratorpedal or a throttle (not shown). For an automatic transmission 36,transmission schedule indicates the conditions under which thetransmission 36 will shift between two gears as a function of thevehicle speed and the pedal or throttle. The throttle is an inputdevice, such as a floor pedal, through which an occupant indicates adesired change in the vehicle acceleration or speed. FIG. 2 shows anexample transmission schedule 202 for an automatic transmission in solidlines. The solid lines indicate the values of vehicle speed and throttleposition at which the transmission 36 will shift between one gear andanother gear; the line marked “2-1” shows the shift from second gear tofirst gear, “1-2” from first to second, “3-2” from third to second, andso on.

As shown in FIG. 4, the vehicle 30 includes sensors 64 configured todetect occupancy of the front seat 52 and of the back seat 54. Thesensors 64 may be visible-light or infrared cameras directed at thefront and back seats 52, 54, weight sensors inside the front and backseats 52, 54, sensors detecting whether a seat belt (not shown) isbuckled or unspooled, or other suitable sensors. The sensors 64 are incommunication with the controller 60 via a network 66. If the vehicle 30is in manual mode, the controller 60 detect that the front seat 52 isnecessarily occupied.

A driver-identification sensor 64 may be in communication with thecontroller 60. The driver-identification sensor 64 may detect an RFID orother signature unique to different keys of the vehicle 30, an input byan occupant of the vehicle 30, biometric data of an occupant of thevehicle 30, or any other suitable indicator of identity for an occupantof the vehicle 30. The identity of an occupant of the vehicle 30 may betied to a classification of that occupant, for example, as a chauffeuror as a non-chauffeur.

As further shown in FIG. 4, the controller 60 is in communication withthe engine 34, the transmission 36, and the torque converter 38. Thecontroller 60 may be a microprocessor-based controller. The controller60 may include a processor, memory, etc. The memory of the controller 60may store instructions executable by the processor.

The controller 60 may transmit and receive signals through thecommunications network 66, such as a controller area network (CAN) bus,Ethernet, Local Interconnect Network (LIN), and/or by any other wired orwireless communications network.

FIG. 5 is a process flow diagram illustrating an exemplary process 500for adjusting the NVH and efficiency characteristics of the vehicle 30based on an occupancy status of the vehicle 30. The process begins in ablock 505, in which the sensors 64 detect occupancy data and thedriver-identification sensor 64 detects driver-identifying data. Forexample, if the sensors 64 are weight sensors, the sensors 64 may detectweight in the back seat 54 but not in the driver or passenger seat 52,53.

Next, in a block 510, the controller 60 receives occupancy data from thesensors 64 and receives driver-identifying data from thedriver-identification sensor 64 via the communications network 66.

Next, in a block 515, the controller 60 determines the occupancy statusof the vehicle 30 based on received sensor data, including the occupancydata and the driver-identifying data. The controller 60 thus detects theoccupancy status of the vehicle 30. The occupancy status may take on oneof multiple statuses. There may be as few as two possible occupancystatuses, or there may be a unique occupancy status for each possibleseating configuration. If the vehicle 30 is an SUV or minivan with eightseats, there may be as many as 2⁸=256 occupancy statuses without usingdriver-identifying data.

For example, the occupancy status may be one of “occupied” and“unoccupied.” The occupancy status is occupied if the occupancy dataindicates that at least one of the seats 52, 53, 54 is occupied. Theoccupancy status is unoccupied if the occupancy data indicates that allthe seats 52, 53, 54 are unoccupied.

For another example, the occupancy status may be one of“front-seat-occupied,” “back-seat-only-occupied,” and “unoccupied.” Theoccupancy status is front-seat-occupied if the occupancy data indicatesthat at least one of the driver seat 52 and the passenger seat 53 isoccupied. The occupancy status is back-seat-only-occupied if theoccupancy data indicates that both the driver seat 52 and the passengerseat 53 are unoccupied and the back seat 54 is occupied. The occupancystatus is unoccupied if the occupancy data indicates that the seats 52,53, 54 are unoccupied.

For a third example, the occupancy status may be one of“driver-seat-occupied,” “passenger-seat-only-occupied,”“back-seat-only-occupied,” and “unoccupied.” The occupancy status isdriver-seat-occupied if the occupancy data indicates that the driverseat 52 is occupied. The occupancy status ispassenger-seat-only-occupied if the occupancy data indicates that thepassenger seat 53 is occupied and the driver seat 52 is unoccupied. Theoccupancy status is back-seat-only-occupied if the occupancy dataindicates that the driver and passenger seats 52, 53 are unoccupied andthe back seat 54 is occupied. The occupancy status is unoccupied if theoccupancy data indicates that the driver, passenger, and back seats 52,53, 54 are unoccupied.

For a fourth example, the occupancy status may be one of“front-seat-occupied,” “chauffeur,” “back-seat-only-occupied,” and“unoccupied.” The occupancy status is front-seat-occupied if theoccupancy data indicates that the driver seat 52 or the passenger seat53 is occupied and the driver-identifying data indicates that anoccupant of the driver or passenger seat 52, 53 is a non-chauffeur. Theoccupancy status is chauffeur if the occupancy data indicates that thedriver seat 52 is occupied, the passenger seat 53 is unoccupied, and thedriver-identifying data indicates that an occupant of the driver seat 52is a chauffeur. The occupancy status is back-seat-only-occupied if theoccupancy data indicates that the driver and passenger seats 52, 53 areunoccupied and the back seat 54 is occupied. The occupancy status isunoccupied if the occupancy data indicates that the seats 52, 53, 54 areunoccupied. The chauffeur and back-seat-only-occupied statuses may betreated as the same occupancy status or as different statuses.

In addition to these three examples, other occupancy statuses and/orcombinations of occupancy statuses are possible.

Next, in a block 520, the controller 60 sets an engine operatingparameter based on the occupancy status. The engine operating parametermay be a parameter of one of the transmission 36 or the torque converter38.

For example, the parameter may be the transmission schedule. Thecontroller 60 may store a different transmission schedule for eachpossible occupancy status. The transmission 36 operates with a lowergear ratio for a given vehicle speed for occupancy statuses with lessstringent NVH requirements. For automatic transmissions, for example,that means that the transmission 36 shifts at lower vehicle speeds foroccupancy statuses with less stringent NVH requirements. For example, asshown in FIG. 2, a transmission schedule 206 for the unoccupied status(in dot-dashed lines) includes each gear ratio at lower speeds of thevehicle 30 than a transmission schedule 204 for theback-seat-only-occupied status (in dashed lines), and the transmissionschedule 204 for the back-seat-only-occupied status includes each gearratio at lower speeds of the vehicle 30 than the transmission schedule202 for the driver-seat-occupied status (in solid lines) as well as thanthe transmission schedule for the passenger-seat-only-occupied status(not shown).

For another example, the parameter may be the lock-up schedule for thetorque converter 38. The controller 60 may store a different lock-upschedule for each status that the occupancy status may take on. Thetorque converter 38 uses lower quantities of slip or more frequentlyenters the locked state for statuses with less stringent NVHrequirements. For example, a lock-up schedule for the unoccupied statushas quantities of slip no higher than, and under at least some vehicleconditions lower than, a lock-up schedule for theback-seat-only-occupied status; and the lock-up schedule for theback-seat-only-occupied status has rates of slip no higher than, andunder at least some vehicle conditions lower than, a lock-up schedulefor the front-seat-occupied status.

Next, in a block 525, the controller 60 controls one of the transmission36 and the torque converter 38 to operate according to the parameter setas described above, that is, the transmission schedule and the lock-upschedule, respectively. The controller 60 may shift the transmission 36according to the transmission schedule for the current occupancy status.The controller 60 may set the quantity of slip of the torque converter38 according to a lock-up schedule for the current occupancy status. Theprocess 500 ends following the block 525.

FIG. 6 is a process flow diagram illustrating an exemplary process 600for adjusting the NVH and efficiency characteristics of the vehicle 30based on an occupancy status of the vehicle 30. The process begins in ablock 605, in which the sensors 64 detect occupancy data and thedriver-identification sensor 64 detects driver-identifying data, asdescribed above with respect to the block 505 of the process 500.

Next, in a block 610, the controller 60 receives occupancy data from thesensors 64 and receives driver-identifying data from thedriver-identification sensor 64 via the communications network 66.

Next, in a block 615, the controller 60 determines the occupancy statusof the vehicle 30 based on received sensor data, including the occupancydata and the driver-identifying data, as described above with respect tothe block 515 of the process 500.

Next, in a block 620, the controller 60 sets the cylinder deactivationschedule based on the occupancy status. The controller 60 may store adifferent cylinder deactivation schedule for each possible occupancystatus and thus select a set of active cylinders 40 from the pluralityof cylinders 40 based on the occupancy status. Cylinder deactivation mayoccur more frequently for statuses with less stringent NVH requirements.For example, as shown in FIG. 3, a region 304 in which some cylinders 40are deactivated may cover more vehicle conditions—specifically, at lowerengine speeds and at higher torques—in the unoccupied status (dashedlines) than the region 302 in the occupied status (solid lines). Inother words, a set of active cylinders 40 for the unoccupied status isno greater than, and for at least some vehicle conditions smaller than,a set of active cylinders 40 for the occupied status. For anotherexample, a set of active cylinders 40 for the unoccupied status is nogreater than, and for at least some vehicle conditions smaller than, aset of active cylinders 40 for the back-seat-only-occupied status; andthe set of active cylinders 40 for the back-seat-only-occupied status isno greater than, and for at least some vehicle conditions smaller than,a set of active cylinders 40 for one of the driver-seat-occupied statusand the passenger-seat-only-occupied status. For a third example, a setof active cylinders 40 for the unoccupied status is no greater than, andfor at least some vehicle conditions smaller than, a set of activecylinders 40 for the chauffeur status; and the set of active cylinders40 for the chauffeur status is no greater than, and for at least somevehicle conditions smaller than, a set of active cylinders 40 for one ofthe driver-seat-occupied status and the passenger-seat-only-occupiedstatus.

Next, in a block 625, the controller activates a set of active cylinders40 and deactivates a remainder of the plurality of cylinders 40according to a cylinder deactivation schedule for the current occupancystatus. The process 600 ends following the block 625.

To execute the exemplary processes 500 and 600, the controller 60 isprogrammed to receive occupancy data from the sensors 64, determine anoccupancy status based on the occupancy data, set an engine operatingparameter of one of the transmission 36 and the torque converter 38based on the occupancy status, select a set of active cylinders 40 fromthe plurality of cylinders 40 based on the occupancy status, control oneof the transmission 36 and the torque converter 38 to operate accordingto the parameter, and activate the set of active cylinders 40 anddeactivate a remainder of the plurality of cylinders 40. The controller60 may be further programmed to determine the occupancy status asoccupied if the occupancy data indicates that at least one of the seats52, 53, 54 are occupied and as unoccupied if the occupancy dataindicates that the seats 52, 53, 54 are unoccupied. Alternatively oradditionally, the controller 60 may be programmed to determine theoccupancy status as driver-seat-occupied if the occupancy data indicatesthat the driver seat 52 is occupied, as passenger-seat-only-occupied ifthe occupancy data indicates that the passenger seat 53 is occupied, asback-seat-only-occupied if the occupancy data indicates that the driverand passenger seats 52, 53 are unoccupied and the back seat 54 isoccupied, and as unoccupied if the occupancy data indicates that theseats 52, 53, 54 are unoccupied. Yet further alternatively oradditionally, the controller 60 may be programmed to determine theoccupancy status as front-seat-occupied if the occupancy data indicatesthat at least one of the driver and passenger seats 52, 53 is occupiedand the driver-identifying data indicates that an occupant of the atleast one of the driver and passenger seats 52, 53 is a non-chauffeur,as chauffeur if the occupancy data indicates that the driver seat 52 isoccupied and the driver-identifying data indicates that an occupant ofthe driver seat 52 is a chauffeur, as back-seat-only-occupied if theoccupancy data indicates that the front seat 52 is unoccupied and theback seat 54 is occupied, and as unoccupied if the occupancy dataindicates that the seats 52, 53, 54 are unoccupied.

The disclosure has been described in an illustrative manner, and it isto be understood that the terminology which has been used is intended tobe in the nature of words of description rather than of limitation. Manymodifications and variations of the present disclosure are possible inlight of the above teachings, and the disclosure may be practicedotherwise than as specifically described.

What is claimed is:
 1. A controller comprising a processor and a memoryfor a vehicle including an engine with a plurality of cylinders, thecontroller programmed to: determine an occupancy status of the vehiclebased on received sensor data, wherein the occupancy status is one of afront-seat-occupied status, a back-seat-only-occupied status, and anunoccupied status; select a set of active cylinders from the pluralityof cylinders based on the occupancy status, wherein a set of activecylinders for the unoccupied status is no greater than, and for at leastsome vehicle conditions smaller than, a set of active cylinders for theback-seat-only-occupied status; and the set of active cylinders for theback-seat-only-occupied status is no greater than, and for at least somevehicle conditions smaller than, a set of active cylinders for thefront-seat-occupied status; and activate the set of active cylinders anddeactivate a remainder of the plurality of cylinders.
 2. The controllerof claim 1, wherein the occupancy status is one of a driver-seatoccupied status, a passenger-seat-only-occupied status, theback-seat-only-occupied status, and the unoccupied status.
 3. Thecontroller of claim 2, wherein a set of active cylinders for theunoccupied status is no greater than, and for at least some vehicleconditions smaller than, a set of active cylinders for theback-seat-only-occupied status; and the set of active cylinders for theback-seat -only-occupied status is no greater than, and for at leastsome vehicle conditions smaller than, a set of active cylinders for oneof the driver-seat-occupied status and the passenger-seat-only-occupiedstatus.
 4. A method of controlling a vehicle including an engine with aplurality of cylinders comprising: detecting an occupancy status of thevehicle, wherein the occupancy status is one of a front-seat-occupiedstatus, a back-seat-only-occupied status, and an unoccupied status;selecting a set of active cylinders from the plurality of cylindersbased on the occupancy status, wherein a set of active cylinders for theunoccupied status is no greater than, and for at least some vehicleconditions smaller than, a set of active cylinders for theback-seat-only-occupied status; and the set of active cylinders for theback-seat-only-occupied status is no greater than, and for at least somevehicle conditions smaller than, a set of active cylinders for thefront-seat-occupied status; and activating the set of active cylindersand deactivating a remainder of the plurality of cylinders.
 5. Themethod of claim 4, wherein the occupancy status is one of a driver-seatoccupied status, a passenger-seat-only-occupied status, theback-seat-only-occupied status, and the unoccupied status.
 6. The methodof claim 5, wherein a set of active cylinders for the unoccupied statusis no greater than, and for at least some vehicle conditions smallerthan, a set of active cylinders for the back-seat-only-occupied status;and a set of active cylinders for the back-seat -only-occupied status isno greater than, and for at least some vehicle conditions smaller than,a set of active cylinders for one of the driver-seat-occupied status andthe passenger-seat-only-occupied status.
 7. A vehicle comprising: anengine including a plurality of cylinders; a controller in communicationwith the engine; a driver seat, a passenger seat, and a back seatcoupled to the engine; and sensors configured to detect occupancy of thedriver seat, of the passenger seat, and of the back seat and incommunication with the controller; wherein the controller is programmedto receive occupancy data from the sensors, determine an occupancystatus of the vehicle based on the occupancy data, wherein the occupancystatus is one of a front-seat-occupied status, a back-seat-only-occupiedstatus, and an unoccupied status, select a set of active cylinders fromthe plurality of cylinders based on the occupancy status, wherein a setof active cylinders for the unoccupied status is no greater than, andfor at least some vehicle conditions smaller than, a set of activecylinders for the back-seat-only-occupied status; and the set of activecylinders for the back-seat-only-occupied status is no greater than, andfor at least some vehicle conditions smaller than, a set of activecylinders for the front-seat-occupied status, and activate the set ofactive cylinders and deactivate a remainder of the plurality ofcylinders.
 8. The vehicle of claim 7, wherein the controller is furtherprogrammed to determine the occupancy status as a driver-seat-occupiedstatus if the occupancy data indicates that the driver seat is occupied,as a passenger-seat-only-occupied status if the occupancy data indicatesthat the passenger seat is occupied and the driver seat is unoccupied,as the back-seat-only-occupied status if the occupancy data indicatesthat the driver and passenger seats are unoccupied and the back seat isoccupied, and as the unoccupied status if the occupancy data indicatesthat the seats are unoccupied.
 9. The vehicle of claim 8, wherein a setof active cylinders for the unoccupied status is no greater than, andfor at least some vehicle conditions smaller than, a set of activecylinders for the back-seat-only-occupied status; and the set of activecylinders for the back-seat-only-occupied status is no greater than, andfor at least some vehicle conditions smaller than, a set of activecylinders for one of the driver-seat-occupied status and thepassenger-seat-only-occupied status.
 10. The vehicle of claim 7, furthercomprising a driver-identification sensor in communication with thecontroller, wherein the controller is further programmed to receivedriver-identifying data from the driver-identification sensor anddetermine the occupancy status based on the driver-identifying data. 11.The vehicle of claim 10, wherein the controller is further programmed todetermine the occupancy status as the front-seat-occupied status if theoccupancy data indicates that at least one of the driver and passengerseats is occupied and the driver-identifying data indicates that anoccupant of the at least one of the driver and passenger seats is anon-chauffeur; as a chauffeur status if the occupancy data indicatesthat the driver seat is occupied, the passenger seat is unoccupied, andthe driver-identifying data indicates that an occupant of the driverseat is a chauffeur; as the back-seat-only-occupied status if theoccupancy data indicates that the driver and passenger seats areunoccupied and the back seat is occupied, and as the unoccupied statusif the occupancy data indicates that the seats are unoccupied.
 12. Thevehicle of claim 11, wherein a set of active cylinders for theunoccupied status is no greater than, and for at least some vehicleconditions smaller than, a set of active cylinders for the chauffeurstatus; and the set of active cylinders for the chauffeur status is nogreater than, and for at least some vehicle conditions smaller than, aset of active cylinders for the front-seat-occupied status.
 13. Thevehicle of claim 11, wherein the chauffeur status and the back-seat-only-occupied status are the same occupancy status.
 14. The controller ofclaim 1, wherein the controller is further programmed to receivedriver-identifying data from a driver-identification sensor anddetermine the occupancy status based on the driver-identifying data. 15.The controller of claim 14, wherein the controller is further programmedto determine the occupancy status as the front-seat-occupied status ifthe occupancy data indicates that at least one of the driver andpassenger seats is occupied and the driver-identifying data indicatesthat an occupant of the at least one of the driver and passenger seatsis a non-chauffeur; as a chauffeur status if the occupancy dataindicates that the driver seat is occupied, the passenger seat isunoccupied, and the driver-identifying data indicates that an occupantof the driver seat is a chauffeur; as the back-seat-only-occupied statusif the occupancy data indicates that the driver and passenger seats areunoccupied and the back seat is occupied, and as the unoccupied statusif the occupancy data indicates that the seats are unoccupied.
 16. Thecontroller of claim 15, wherein a set of active cylinders for theunoccupied status is no greater than, and for at least some vehicleconditions smaller than, a set of active cylinders for the chauffeurstatus; and the set of active cylinders for the chauffeur status is nogreater than, and for at least some vehicle conditions smaller than, aset of active cylinders for the front-seat-occupied status.
 17. Thecontroller of claim 15, wherein the chauffeur status and theback-seat-only -occupied status are the same occupancy status.
 18. Themethod of claim 3, further comprising receiving driver-identifying datafrom a driver-identification sensor and determining the occupancy statusbased on the driver-identifying data.
 19. The method of claim 18,further comprising determining the occupancy status as thefront-seat-occupied status if the occupancy data indicates that at leastone of the driver and passenger seats is occupied and thedriver-identifying data indicates that an occupant of the at least oneof the driver and passenger seats is a non-chauffeur; as a chauffeurstatus if the occupancy data indicates that the driver seat is occupied,the passenger seat is unoccupied, and the driver-identifying dataindicates that an occupant of the driver seat is a chauffeur; as theback-seat-only-occupied status if the occupancy data indicates that thedriver and passenger seats are unoccupied and the back seat is occupied,and as the unoccupied status if the occupancy data indicates that theseats are unoccupied.
 20. The method of claim 19, wherein a set ofactive cylinders for the unoccupied status is no greater than, and forat least some vehicle conditions smaller than, a set of active cylindersfor the chauffeur status; and the set of active cylinders for thechauffeur status is no greater than, and for at least some vehicleconditions smaller than, a set of active cylinders for thefront-seat-occupied status.